(c)
Required area
$= 2\int_{- 1}^{3}{\sqrt{x^{2} - 1}\ dx}$
$= 2\left\lbrack \frac{x\sqrt{x^{2} - 1}}{2} - \frac{1}{2}\log{|x + \sqrt{x^{2} - 1}} \right\rbrack_{- 1}^{3}$
$= \left( x\sqrt{x^{2} - 1} - \log{|x +}\sqrt{x^{2} - 1}| \right)_{- 1}^{3}$
$= 6\sqrt{2} - \log{|3 + 2\sqrt{2}|}$